This invention is directed toward a servo piston and more particularly a low friction compact servo piston assembly for swashplate style hydrostatic pumps and motors.
Servo pistons are well known in the art. Typically, servo pistons and their connection to a swashplate are designed to minimize the reaction forces between the servo piston and it's guiding bore to reduce the frictional force resisting the piston's motion. This frictional force is a significant contributor to hysteresis in piston position as commanded by the displacement control system. Friction between the piston and it's guiding bore also lead to wear and reduced component life.
With transverse axis servo pistons, where the servo piston axis is perpendicular to shaft axis, it is typical to use cradle type swashplate bearings instead of 360° bearings. While the servo piston may occupy the vacated space of the 360° bearing, the disadvantage is that the cradle type bearings are custom and more expensive than standard catalog bearings.
In order to use standard bearings and still meet power density requirements, the servo piston must be designed to make use of available space. Therefore a need exists in the art for a device that addresses these deficiencies.
An objective of the present invention is to provide a servo piston assembly that is compact and low friction.
Another objective of the present invention is to provide a servo piston assembly that is inexpensive to manufacture.
These and other objectives will be apparent to one skilled in the art based upon the following written description, drawings, and claims.